They both had egos, so I can't say that Jimmy is blameless.
But Jerry is and has been the biggest problem with this franchise. Honestly, if he'd step aside, he could probably pull any number of qualified GM candidates. I think he does a great job as a pure owner. He makes the team a ton of money and he's a salesman.
He just has no business dealing with the football side of things.
Even Garrett is an ego thing for him. I like Garrett, but was he qualified to be a HC yet? No. Even a guy like Mike Tomlin had way more coaching experience than Garrett when he started. But Jerry wants to take credit for finding the next great coach.
Meanwhile, people like Hostile want to try to pretend that Garrett is HC, OC and de facto GM when the guy has proven he doesn't have enough coaching experience to completely have a handle on simple clock management.